1. Technical Field
The present invention relates to a power amplifier circuit.
2. Background Art
In a mobile communication device such as a mobile phone, a power amplifier circuit is used to amplify power of a signal to be transmitted to a base station. In recent years, modulation systems such as a high speed uplink packet access (HSUPA) system, a long term evolution (LTE) system, and an LTE-Advanced system, which are high-speed data communication standards, are employed by mobile phones. In such communication standards, in order to enhance a communication speed, it is important to reduce unevenness in phase or amplitude. That is, high linearity is desirable for the power amplifier circuit. In such communication standards, in order to enhance a communication speed, a range (dynamic range) in which an amplitude of a signal varies may often be broadened. In order to enhance linearity when the dynamic range is broad, a high source voltage is desired and thus power consumption in the power amplifier circuit tends to increase.
On the other hand, in a mobile phone, a decrease in power consumption is desirable for extending an available time for calling or communication. For example, Patent Document 1 discloses an envelope tracking system which can achieve enhancement of power efficiency by controlling a source voltage of a power amplifier circuit depending on an amplitude level of an input modulation signal.